The objectives of this Phase I, dose-escalating, long-term tolerance study are to evaluate the pharmacokinetics of oral ganciclovir in HIV-infected infants, children and adolescents, to determine its maximum tolerated dose in these subjects, and to evaluate its long-term safety and tolerance in them. It will also evaluate the effect of oral ganciclovir on the virologic parameters of cytomegalovirus (CMV), i.e., viral load, shedding and resistance to ganciclovir.(ACTG 226)